Digital acquisition devices, such as the Tektronix TLA7000 Logic Analyzer, enable electrical engineers to measure the signals produced by the digital systems that they design. Research labs use digital acquisition devices to observe correctness of timing and intensity of signals in microprocessors, memory, buses, and other components of digital systems. Acquisition devices play a major role in the development of the continually advancing electronics industry.
A digital acquisition device will typically display a sensed signal as a sharply elevated or descending step. The rise from “off” to “on” and the descent from “on” to “off” is usually synchronized with the period of a clock in the system under test, and the transition from one state to the other is represented visually as a vertical edge. It is useful to distinguish the clock of a system under test from a clock of a digital acquisition device.
In order to provide high resolution on the signal under test, the sample clock of the digital acquisition device must pulse, and therefore sample the signal under test, at a frequency higher than the frequency of the tested system's clock. This yields meaningful measurements to engineers using the acquisition device. The distance between two consecutive pulses of the clock for the digital acquisition device may be referred to as a sampling bin, and the pulse itself is the sampling bin boundary. A rising or falling edge in an ideal scenario will consistently land within a single sample bin and, therefore. will be consistently associated with a single sample clock edge.
When testing a particular design, engineers sometimes measure a signal occurring in a repeated pattern. The acquisition device may be programmed to begin data acquisition with a trigger, which can itself be a rising or a falling edge. By supplying a repeating input, engineers can observe whether an input predictably and reliably generates a consistent output. Under ideal circumstances, the output is displayed as a static series of steps if the device is working as expected. Circumstances, however, are not always ideal.
Use of Digital Edge Averaging (DEA) on a set of digital signals can eliminate jitter-related chatter while simultaneously increasing the timing accuracy of the edges beyond the abilities of the base acquisition system. However, DEA alone requires that all edges on all digital signals be Uniformly Synchronous (US) to the trigger event. That is, a DEA representation of any single transition can only be calculated if that edge occurs within a DEA aperture in every repeated acquisition.
Accordingly, there remains a need for improved methods for presenting a waveform on a digital acquisition device.